Showing papers in "Vehicle System Dynamics in 1978"
TL;DR: In this paper, a strategy model based on vehicle constraints and known human operator characteristics is proposed for describing behavior in the lane-keeping task, which includes nonlinear thresholds operating on vehicle yaw and lateral translation, random input sources to account for spurious driver activity, and smoothing to adjust driver response lag.
Abstract: SUMMARY Based on vehicle constraints and known human operator characteristics, a strategy model was postulated for describing behavior in the lane keeping task. This model includes nonlinear thresholds operating on vehicle yaw and lateral translation, random input sources to account for spurious driver activity, and smoothing to account for driver response lag. The output of the model is steering wheel position To determine model parameters and model suitability in describing driver behavior, recordings were made for driver-subjects performing a lane-keeping task in a moving base driving simulator having a computer generated display. A procedure involving both analytic and experimental techniques was then developed for determining the model parameters of each driver Statistical comparisons and visual inspections made between driver-vehicle and model-vehicle time histories indicate a high degree of correspondence. Models such as these show promise in obtaining a better understanding of driver behavior and ...
29 citations
TL;DR: In this paper, the nature and magnitude of the component of propulsive force associated with these energy loss mechanisms were estimated using elementary vehicle models, and the force was found to vary dramatically with speed for several types of periodic roadway profiles studied.
Abstract: Vehicles which travel on uneven roadways or rough surfaces require power beyond that associated with air drag, rolling resistance or other sources of friction even though kinetic and potential energy may be conserved on the average. This is true because damped relative motions within the vehicle dissipate energy, and, even for nearly rigid vehicles, energy is lost at impact with the ground whenever the vehicle loses contact with the ground surface due to the finite downward acceleration of gravity. Using elementary vehicle models, the nature and magnitude of the component of propulsive force associated with these energy loss mechanisms is estimated. In certain speed ranges, this force is found to vary dramatically with speed for several types of periodic roadway profiles studied. While the force due to unevenness may be small compared to other forces for high-speed vehicles operating on smooth surfaces, it can be the major source of required power for off-road vehicles operating on very rough terrain. /Author/TRRL/
26 citations
TL;DR: In this article, the elastic stiffness matrix, which describes the nature and configuration of the suspension elements connecting the various bodies, must satisfy in order to achieve both perfect steering on circular curves and dynamic stability.
Abstract: SUMMARY The general form of the equations o f motion o f multi-body articulated railway vehicles are used to establish the conditions which the elastic stiffness matrix, which describes the nature and configuration o f the suspension elements connecting the various bodies, must satisfy in order to achieve both perfect steering on circular curves and dynamic stability. The resulting criteria are then used to discuss the properties of various multi-axle configurations which are either typical of current practice or possibilities for future designs.
22 citations
TL;DR: In this paper, the normal mode dynamic behavior of uniform Bernoulli-Euler beams is represented by a bond graph model and the resulting overall system bond graph is shown to yield the governing state equations in a straightforward manner.
Abstract: SUMMARY Bond graph modeling techniques are used to represent the normal mode dynamic behavior of uniform Bernoulli-Euler beams. The independent beam models are then coupled together to form a distributed system structure of arbitrary complexity. The resulting overall system bond graph is shown to yield the governing state equations in a straightforward manner. Then, through proper ordering of the equations, the normal modes and frequencies of the coupled system are easily obtained This procedure is demonstrated for a vehicle A-frame structure. In addition, the bond graph model is modified to include primary and secondary suspension dynamics.
19 citations
TL;DR: In this paper, the transmission of road-generated vibrations into a vehicle body is treated as a source-path-receiver problem and a mathematical model is derived for such a system which would enable detailed parameter investigation to be undertaken using the gradient method of optimization.
Abstract: SUMMARY The transmission of road-generated vibrations into a vehicle body is treated as a source-path-receiver problem. The suspension system acts as the path, and improved isolation can be achieved by having a single compliant bushing at the connecting point of the shock absorber to the body with none at the other end. A mathematical model is derived for such a system which would enable detailed parameter investigation to be undertaken using the gradient method of optimization. An expression for the absolute displacement transmissibility of the body is derived and the optimization procedure is applied in order to evaluate the optimum values of the non-dimensional variables involved. This minimizes the maximum motion transmitted to the body from the road surface over a broad frequency range. Design data which are presented non-dimensionally for parameter variations show the influence of three variables: the bushing stiffness, the resonant frequency ratio and the damping coefficient upon the transmissibility.
16 citations
TL;DR: In this paper, an alternative procedure is developed which allows direct computation of mean square values and correlations of system variables for both transient and steady-state conditions, based upon the differential equation for the covariance matrix which is directly related to the state equations for the vehicle.
Abstract: SUMMARY Dynamic response calculations for vehicles traversing irregular surfaces are usually accomplished using frequency domain methods involving spectral densities and transfer functions. Here an alternative procedure is developed which allows direct computation of mean square values and correlations of system variables for both transient and steady-state conditions. The method is based upon the differential equation for the covariance matrix which is directly related to the state equations for the vehicle. Multiple white noise inputs can be incorporated as well as inputs at two wheels which follow the same track at a distance from one another..The method is suitable for computer implementation without the complex algebra associated with finding all necessary transfer functions and the necessity of evaluating integrals in order to find mean square values using the conventional approach. As an illustration, a simple vehicle model is worked out completely and the variation of pitch and heave motion as a f...
12 citations
TL;DR: In this paper, the spectral densities of the left and right longitudinal track and their statistical dependence were used to calculate the vehicle response to road-surface irregularity inputs, and the dynamic tire load showed that independent suspension systems are more advantageous than beam axles.
Abstract: SUMMARY Measurement of two track road inputs and theoretical application of the results The calculation of vehicle response to road-surface irregularity inputs requires the spectral densities of the left and right longitudinal track and their statistical dependence This paper presents some resluts of parallel profile measurements, three typical german roads have been chosen Random vibration of two vehicle types are digital-simulated. The dynamic tire load shows that independent suspension systems are more advantageous than beam axles, because by wheel tramp this type increases the dynamic tire load.
12 citations
TL;DR: In this article, a combination of the steepest descent method and the Davidon Fletcher Powell method is used to solve the problem of optimal braking on a tractor-semitrailer.
Abstract: SUMMARY This paper is concerned with the braking performance and the handling behavior of the tractor-semitrailer truck under optimal braking. Optimal control theory is used in order to deal with the problem and a combination of the steepest descent method and the Davidon Fletcher Powell method is used to solve it numerically. Results for some chosen braking maneuvers are obtained for a nonlinear truck model which has 14 degrees of freedom. These results show that, for the chosen maneuvers an idealized anti-skid braking is close to being optimal in the sense defined in this paper. Implementation of an idealized anti-skid braking on the tractor-semitrailer truck, however, may be not desirable.
8 citations
TL;DR: In this article, the authors applied the known power spectra of the random road roughness to the suspension behavior of a four-wheeled vehicle, each of the four vertical input signals together with their related interdependence are considered, if exact results are to be obtained.
Abstract: SUMMARY When applying the known power spectra of the random road roughness to the suspension behaviour of a four-wheeled vehicle, each of the four vertical input signals together with their related interdependence are to be considered, if exact results are to be obtained. The correlations are determined by way of calculation. The resulting roughness spectra of bounce, pitch, roll and torsional excitations will be applied to various vehicles, characterized by different design parameters. By means of a three-dimensional simulation model the virtual values of the random vehicle vibrations are calculated, while determining at the same time the influence of vehicle speed, waviness exponent, track width, wheel base, and axle design feature as well as the relationship between the vertical vibrations and the reference point in the vehicle body.
7 citations
TL;DR: Parkhilovskii et al. as discussed by the authors proposed a model based on isotropy for profile-pair description of road surfaces and compared it with the Parkhilvskii model for describing a road surface.
Abstract: Models of road surfaces to be used as a basis for vehicle response determination must - at least implicitly - define both direct and cross spectral densities for the profiles of pairs of parallel tracks. The model proposed by Parkhilovskii is here compared with that based on isotropy. It is shown that, despite apparent shortcomings, the Parkhilovskii model is fully compatible with the isotropy model for profile-pair description, and that the two may helpfully be used together in describing a road surface.(a) /TRRL/
5 citations
TL;DR: In this article, the authors deal with the simulation of the behaviour of tractor-semitrailer vehicles at braking on wet, slippery road surface and show the influence of cornering on the behaviour during braking in a turn.
Abstract: SUMMARY Simulation of Steering and Braking Behaviour of Tractor-Semitrailer Vehicles in Extreme Situations This paper deals with the simulation of the behaviour of tractor-semitrailer vehicles at braking on wet, slippery road surface. The nonlinear model used for the computation enables to simulate extreme situations at wheel locking and swerving The instabilities during braking such as jackknifing and trailer swing as well as non steerability are investigated. Straightline braking shows the influence of cornering on the behaviour during braking in a turn.
TL;DR: In this article, the effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers are examined and the way in which the correct locking sequence may be achieved is also discussed in detail.
Abstract: SUMMARY It is known that loss of directional stability during braking occurs in many road accidents involving tractor-semitrailers. To minimize the undesired directional response, the correct order of locking of the wheels is of importance and should receive greater attention. This paper examines the effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers. The way in which the correct locking sequence may be achieved is also discussed in detail.
Journal Article•
TL;DR: In this paper, the simulation of the behaviour of tractor-semitrailer vehicles at braking on wet, slippery road surface is presented, which enables a user to simulate extreme situations at wheel locking and swerving.
Abstract: This paper deals with the simulation of the behaviour of tractor-semitrailer vehicles at braking on wet, slippery road surface. The nonlinear model used for the computation enables a user to simulate extreme situations at wheel locking and swerving. The instabilities during braking such as jackknifing and trailer swing as well as non steerability are investigated. Straightline braking shows the influence of cornering on the behaviour during braking in a turn. /TRRL/
TL;DR: In this paper, the idea of a passive safety belt operated solely by the motor car's door has been rigorously analyzed on a mathematical model and an optimal configuration of the device was produced and a working model built, based on the analytically obtained design specifications.
Abstract: SUMMARY The idea of a passive safety belt operated solely by the motor car's door has been rigorously analysed on a mathematical model. By calculation methods, an optimal configuration of the device was produced and a working model built, based on the analytically obtained design specifications. The model proved the feasibility and advantages of the proposed system, which is based on the conventional 3-point safety-belt design and utilises existing car structures.
TL;DR: In this paper, an investigation was carried out to determine the origins of vibration of an automobile rear axle with the object of establishing the significance of road-surface-induced vibratory inputs.
Abstract: SUMMARY An investigation was carried out to determine the origins of vibration of an automobile rear axle with the object of establishing the significance of road-surface-induced vibratory inputs. This was achieved by measuring the vibratory acceleration of the rear axle of an automobile as it traverses straight sections of typically paved roads, at uniform speeds, then comparing the results with those obtained by laboratory simulation. The investigation revealed significant levels of vertical, longitudinal and, to a much lesser extent, lateral vibrations. The main source of vertical vibrations is shown to be induced mainly by vertical displacements imposed by the road-surface irregularities on the vehicle tyres. The longitudinal and lateral components are shown to be induced mainly by the engine and the drive-line (including tyre/wheel assemblies) as well as due to coupling between the vertical, longitudinal and lateral motions of the rear axle imposed by the geometry of the rear axle suspension.